Assume a parent isotope has a half-life of 100 million years. How old is a sample that
contains 15% of its original parent isotope?
250 million years
270 million years
200 million years
100 million year
Answers
Answer:
270 million
Explanation:
1/2 ^n = .15 (.15 is 15% in decimal)
log both sides
n log (1/2) = log (.15 )
n = 2.737 half lives
EACH half life is 100 million
2.737 * 100 million = 273.7 million
Related Questions
In one to two sentences, describe an experiment that would show that intramolecular forces (attractions between atoms within molecules) are stronger than intermolecular forces (attractions between molecules).
thank you !!
Answers
short story about The Blind Date by Jeffrey Archer
What is the nuclear equation for decay of Am - 241
Answers
Americium is a radioactive element .
It goes through alpha decay during nuclear reactions .The nuclear reaction.is given by
[tex]\rm {}^{241}_{95}Am\longrightarrow {}^{237}_{93}Np+{}^4_2\alpha[/tex]
Np stands for NuptuniumHere alpha can be written as He too
how can you explain that even though you continue to add pure water into a substance, even though the resultant ph might differ a little, the acidity or alkalinity of substance still remains the same to that of substance?
Answers
Addition of pure water does not change pH of a solution because pure water has neutral pH.
Why the pH does not change when pure water is added?Even though you continue to add pure water into a substance, the acidity or alkalinity of substance still remains the same to that of substance because pure water has neutral pH which can't change the acidity or alkalinity of a solution.
So we can conclude that addition of pure water does not change pH of a solution because pure water has neutral pH.
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A chemical reaction can be reversed if?
The energy of the products exceeds the activation energy threshold.
The energy of the reactants exceeds the activation energy threshold.
The energy of the products is less than the activation energy threshold.
The energy of the reactants is less than the activation energy threshold.
Answers
Chemical reaction can be reversed if the energy of the reactants is less than the activation energy threshold.
What is a reversible reaction?A reversible reaction is a reaction in which the conversion of reactants to products and the conversion of products to reactants occur simultaneously.
Conditions for reversible reactionIn equilibrium reaction, the activation energy of the forward reaction is more than that of backward reaction which causes bond breakage of the reactants.
Activation energy = (Threshold energy) - (Internal energy of the reactants)
Thus, a chemical reaction can be reversed if the energy of the reactants is less than the activation energy threshold.
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During dehydration synthesis, an enzyme removes a ____________ functional group from the monomers of one organic molecule and a hydrogen from another monomer, linking monomers together to form a ____________ . This chemical reaction also forms ____________ .
Answers
Linking monomers together to form a polymer .This chemical reaction also forms water molecules.
What is Polymerization?This is a type of reaction which involves the linking of two or more monomers to form a polymer.
Dehydration reaction forms water molecules as part of the product thereby making it the most appropriate choice.
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G.P.E. on Earth is determined by an object's _______and _______
Answers
Answer:
mass and height of the object.
You can make a solution (solid solute) more concentrated by
adding more solute
O increasing the pressure
adding more water
adding more solvent
Answers
Answer:
increasing the pressure
Explanation:
You can make a solution more concentrated by increasing the pressure.
Sample Response: Forces are either positive or negative vectors, depending on the direction in which the force is acting. The net force is the sum of all of the forces acting on an object. If the children pull on the toy with the same force in opposite directions, the forces will be perfectly balanced and cancel out, leaving a net force of zero.
What did you include in your response? Check all that apply.
Forces are vectors.
Forces can be positive or negative.
The forces exerted by the children are in balance.
The net force is the sum of all of the forces that canceled out to zero.
Answers
The net force is the sum of all of the forces that cancelled out to zero. Hence, option D is correct.
What is force?The pushes or pulls on an object with mass causes it to change its velocity.
The net force is the vector sum of all forces acting on an object. Force is a vector quantity.
Two forces of equal magnitude when acting on an object in opposite directions will cancel out each other.
As a result net force is equal to 0. The word net here shows the total force acting on the object.
Hence, option D is correct.
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What is force?
The pushes or pulls on an object with mass causes it to change its velocity.The net force is the vector sum of all forces acting on an object. Force is a vector quantity. Two forces of equal magnitude when acting on an object in opposite directions will cancel out each other. As a result net force is equal to 0. The word net here shows the total force acting on the object.Hence, option D is correct.
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help help help help help help
Answers
The exercise requires you to complete the sentences using the drop down. The complete sentences are given below.
Which step in the design process is represented by each of the following?The topic that was chosen because many students experienced cracked cell phone screens is: Protecting Cell Phones;Discussing ideas for possible cell phone cases: Phones that are durable;Writing down their list of requirements needed to make the phone case: Colorful and funky.Learn more about completing sentences at:
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if this strand is replicated what is the complementary strand that is produced
Answers
Answer:
During DNA replication, each of the two strands that make up the double helix serves as a template from which new strands are copied. The new strand will be complementary to the parental or “old” strand. Each new double strand consists of one parental strand and one new daughter strand.
Explanation:
hope it helps you
How many moles of a gas are contained in 2.085 L at STP?
A. 0.0931 mol
B. 10.8 mol
C. 10.3 mol
D. 1.11 mol
Answers
A.0.0931 mol
from ideal gas equation ,
We have ,
PV = nRT
Where P stands where pressure of gas.
We know that pressure of gas at STP = 1 atm
V stands for volume of gas , given Volume is 2.085 L
R stands for gas constant , R = 0.0821
And T stands for absolute temperature and measured in kelvin,T=273K
Now ,
PV = nRT
n = PV/RT
Refer attachment for working
how do you treat a sulfuric acid burn with sodium hydroxide
Answers
1. If the pressure of a fixed volume of gas decreased in a sealed container, what variable would you think changed? did this variable increase or decrease?.
Answers
Answer:
Temp decreased
Explanation:
If the container is sealed and the pressure DEcreases, then the temperature DEcreased
PV = n RT n R V are constant if P goes down then so does T
The pressure of x ml of a gas was increased from 2 atm to 4 atm at constant temperture. what will be the new volume?
Answers
The new volume of the gas given the data from the question is 1/2X mL
Data obtained from the question
Initial volume (V₁) = X mL
Initial pressure (P₁) = 2 atm
New pressure (P₂) = 4 atm
New Volume (V₂) = ?
How to determine the new volume
The new volume of the gas can be obtained by using the Boyles’ law equation as illustrated below:
P₁V₁ = P₂V₂
2 × X = 4 × V₂
2X = 4V₂
Divide both side by 4
V₂= 2X / 4
V₂ = 1/2X mL
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Scientists made the following two observations about emission spectra: each element has a unique emission spectrum. atoms emit energy only at specific wavelengths. describe how the bohr model explains both of these observations.
Answers
In this model, electrons are found on unique levels and when jumping from one level to another, electrons emit light at a specific wavelength.
What is the Bohr model?The Bohr model is an atomic model describing the properties of atoms and their constituents (electrons).
This model states different atoms have specific levels of energy where electrons can be located.
In conclusion, in this model, electrons are found on unique levels and when jumping from one level to another, electrons emit light at a specific wavelength.
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Answer:
In the Bohr model, electrons can exist only in certain energy levels surrounding the atom. The energy levels in each atom are unique. When electrons jump from a higher energy level to a lower one, they emit light at a wavelength that corresponds to the energy difference between the levels.
Explanation:
Ed22
A solid chloride E which sublimes on heating reacted with an alkali F to give a choking gas G.G turns red litmus paper blue . identify E, F and G
Answers
Answer:
E:ammonium chloride
F:sodium hydroxide
G:ammonia
if 4.50 mol of ethane, c_(2)h_(6),undergo combustion according to the equation below , how many moles of oxygen are required? 2C_(2)H_(6)+7O_(2 )->4CO_(2)+6H_(2)O
Answers
15.75 moles of oxygen is required for 4.5 mole of ethane.
What is a Combustion Reaction ?The reaction in which a fuel gets oxidized by an oxidizing agent is called a Combustion Reaction , releasing a large amount of energy is called Combustion Reaction.
It is given in the question that
4.50 mole of ethane undergoes Combustion
2C₂H₆ + 7O₂ -> 4CO₂ +6H₂O
Mole fraction of ethane to oxygen is 2:7
Moles of ethane = 4.5
4.5 /x = 2/7
4.5 * 7 / 2 = x
x = 15.75 moles.
Therefore 15.75 moles of oxygen is required for 4.5 mole of ethane.
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9. (05.06 mc)
during an experiment, the percent yield of calcium chloride from a reaction was 80.34%. theoretically, the expected amount should have been 115 grams. what was the actual yield
from this reaction?
caco, + hc - cacl + co, + h20 (5 points)
a. 090.1 grams
b. 92.4 grams
c. 109.2 grams
d. 115.3 grams
Answers
The actual yield of the experiment given the data from the question is 92.4 g (Option B)
What is percentage yield?This is the ratio of the actual yield to the theoretical yield of a given reaction multiplied by 100
Percentage yield = (Actual / Theoretical) × 100
What is actual yield?This is the amount obtained from the expriment procedures
What is theoretical yield?This is the amount obtained from simple calculations as regarding the experiment.
How to determine the actual yieldPercentage yield = 80.34%Theoretical yield = 115 gActual yield =?Actual yield = percentage yield × theoretical yield
Actual yield = 80.34% × 115
Actual yield = 0.8034 × 115
Actual yield = 92.4 g
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how many grans of NaoH Are needed to neutralize grans of H2So4
Answers
Answer :]
to convert from g NaOH to mol NaOH. = 1.48 g NaOH are needed to neutralize the acid.
What is the mass in grams of each of the following?
a.) 6.02 x 1024 atoms Bi
c.) 6.02 x 1022 atoms He
e.) 6.02 x 10¹5 atoms U
b.) 1.00 x 1024 atoms Mn
d.) 6.02 x 10¹5 atoms N
Answers
Answer:
a. 208g Bi
c. 0.0400g He
e. 2.38g U
b. 9.12g Mn
d. 1.40g N
Explanation:
I apologize in advance if any are incorrect. Hopefully this helps.
How to draw ethyl pentanoate?
Answers
Which radioisotope is used to treat thyroid disorders?.
Answers
Answer:
I-123 and I-131
Explanation:
Radioactive iodine takes advantage of the fact that thyroid cells and thyroid cancer cells absorb iodine; therefore, it has been used to diagnose or treat various thyroid disorders. Iodine is made into two radioactive isotopes, I-123 and I-131, that are commonly used in patients with thyroid disease.
4. What is a homogeneous solution? Give an example.
Answers
Answer:
Homogeneous solutions are solutions with uniform composition and properties throughout the solution.
Explanation:
For example a cup of coffee, perfume, cough syrup, a solution of salt or sugar in water, etc. Heterogeneous solutions are solutions with non-uniform composition and properties throughout the solution.
Answer:
A homogeneous mixture is a mixture in which the composition is uniform throughout the mixture. Example: The salt water is homogeneous because the dissolved salt is evenly distributed throughout the entire salt water sample. Another examples are wine, blood, vinegar
Explanation:
Common Tasks for Chemists.
Answers
Answer:
analysis organic and inorganic compounds,refine substances and chemicals products
How can you measure the volume of air inside of a balloon?
Answers
You could let the air out of the balloon while it is under the water with a container filled with water upside down over it. And measure the water displacement.
Balance the following redox reaction if it occurs in acidic solution. What are the coefficients in front of h2c2o4 and h2o in the balanced reaction? mno4⁻(aq) h2c2o4(aq) → mn2 (aq) co2(g)
Answers
The balanced redox reaction, if it occurs in acidic solution, is
5C₂O₄²⁻(aq) + 2MnO₄⁻(aq) + 16H⁺-----> 10CO₂(g) + 2Mn²⁺(aq) + 8H₂O(l)
What are redox reaction?Redox reactions are those in which loss and again of electrons occur.
To balance the redox reaction, we must first break the whole reaction into half equations;
Oxidation half equation
[tex]\rm 5C_2O4^2^-(aq) + 10e + 8H^+----- > 10CO_2(g) + 4H_2O(l)[/tex]
Reduction half equation
[tex]\rm 2MnO_4^- (aq) + 10e + 8H^+----- > 2Mn^2+(aq) + 4H_2O(l)[/tex]
Now combine both the reactions
[tex]\rm 5C_2O_4^2-(aq) + 2MnO4^- (aq) + 16H^+----- > 10CO_2(g) + 2Mn^2+(aq) + 8H_2O(l)[/tex]
Thus, the coefficient of H₂C₂O₄ is 5 and that of water is 8.
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Name and Title:
Include your name, instructor's name, date, and name of lab.
Objectives(s):
In your own words, what is the purpose of this lab?
Hypothesis:
In this section, please include the predictions you developed during your lab activity. These statements reflect your predicted outcomes for the experiment.
Procedure:
The materials and procedures are listed in your virtual lab. You do not need to repeat them here. However, you should note if you experienced any errors or other factors that might affect your outcome. Using your summary questions at the end of your virtual lab activity, please clearly define the dependent and independent variables of the experiment.
Data:
Record the elements present in each unknown astronomical object. Be sure to indicate “yes” or “no” for each element.
Hydrogen Helium Lithium Sodium Carbon Nitrogen
Moon One
Moon Two
Planet One
Planet Two
Conclusion:
Your conclusion will include a summary of the lab results and an interpretation of the results. Please answer all questions in complete sentences using your own words.
Using two to three sentences, summarize what you investigated and observed in this lab.
Astronomers use a wide variety of technology to explore space and the electromagnetic spectrum; why do you believe it is essential to use many types of equipment when studying space?
If carbon was the most common element found in the moons and planets, what element is missing that would make them similar to Earth? Explain why. (Hint: Think about the carbon cycle.)
We know that the electromagnetic spectrum uses wavelengths and frequencies to determine a lot about outer space. How does it help us find out the make-up of stars?
Why might it be useful to determine the elements that a planet or moon is made up of?
Answers
Answer:
I don't no this answer do you know then telle
A solvent is added to dissolve only one mixture component and then the liquids are separated. Choose... A liquid is carefully poured out, leaving the solid behind in the container. Choose... A solid is caught on paper or a membrane while the liquid passes through. Choose... A solid mixture is heated. One component transitions directly between solid and gas. Choose...
Answers
The solid would be caught on a filter paper or membrane while the liquid passes through.
FiltrationFiltration is used to separate a mixture of insoluble substances in a liquid.
Since the aim is to separate the insoluble component of the mixture from the liquid, filtration using a suitable filter paper or membrane will be the way out.
The liquid will pass through the filter paper or the membrane while the insoluble component will be caught. This can then be dried and collected accordingly.
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2. Qualitative observations are ______. based on your senses measurable often taken using instruments only made by scientists in a laboratory
Answers
Qualitative observations are research methods based on your senses measurable often taken using instruments only made by scientists in a laboratory
What are Qualitative Observations ?The research method in which the data is collected either by using the five senses or by measurements, In this the qualities of the substance matter and not the quantity.
The qualitative observation is subjective and so varies from person to person.
Each research using the qualitative observation will be unique.
The data is collected using one to one interaction , by questionnaires , The data is non-numerical.
Qualitative observations are research methods based on your senses measurable often taken using instruments only made by scientists in a laboratory
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What do esters aldehydes and ketones all have in common? (Look back at
table R and be specific!)